Solenoid



v Sept. 17, 1946. 1.. M. PERSONS SOLENOID Filed Jan. 11, 1943 FIG. 1.

FIG. 2;

w .-w m RR 5 m M MM w E T MM 4 M m m m L Patented Sept. 17, 1946 UNITED STATES PATENT OFFICE SOLENOID Lawrence M. Persons, Ladue, M0., assignor to Me- Quay-Norris Manufacturing Company,

Claims.

This invention relates generally to electro-magnets and particularly to solenoids of the character wherein a movable armature travels axially of the coil upon energization of the latter so as to deliver a power impulse to some device being actuated thereby.

In solenoids of the character referred to, it has heretofore been proposed to chamfer one end of the movable armature and to provide a corresponding chamfer on a stationary core piece toward which the chamfered surface of the movable armature is intended to approach upon the energization of the electro-magnet.

The object of the present invention is to im prove the efficiency of solenoids of the character referred to and in particular to achieve a greater power out-put per unit of power in-put than has heretofore been accomplished.

Other objects of the invention will become ap parent to those skilled in the art when the following description is read in connection with the accompanying drawing in which:

Figure l is a longitudinal sectional View of an electro-magnet constructed in accordance with the present invention.

Figure 2 is a perspective view of the movable armature member utilized in the device of Fi ure 1, part being broken away to reveal the shape and arrangement of parts.

In accordance with the present invention solenoids of the character above referred to which have heretofore been provided with a chamfered armature arranged to approach a correspondingly chamfered stationary core piece have their movable armature and stationary core pieces provided with specially shaped cooperating projections and recesses. More particularly the present invention contemplates that, instead of providing the movable armature and stationary core pieces of such solenoids with cooperating chamiered surfaces, one of said parts is provided with a doubly tapered projection and the other with a doubly tapered complemental recess adapted to receive the projection on the first part, upon energization of the device. In such arrangement it is possible to vary the load characteristics of the device by a variation in the angle of taper, the length of taper, and the width of the face constituting the tip of the projection (and the bottom of the recess) so as to readily adapt the device to load idiosyncracies of its intended application. In any event, however, the maximum mean force is delivered when the tapered surfaces depart from parallel with the direction of travel of the armature at between 8 and 15 degrees so long as the tip of the projection of the bottom of the recess remain blunt, that is, of substantial surface area transverse to the direction of the travel of the armature.

The present invention further contemplates a construction and arrangement of the parts including the core pieces, the armature and an encasing magnetic shell so that maximum flux density in the magnetic circuit occurs in the region of the cooperating doubly tapered surfaces.

Referring now to Figure 1 of the drawing for an illustrative embodiment of the invention, the solenoid may comprise a coil 1 of any desired number of turns, one end of which is connected to a terminal post 2 and the other end to another terminal post 3. The coil I is wound upon a spool 4 of insulating material and within the center opening of the spool 4 is arranged a stationary core piece or yoke 5 extending for part only of the axial length of the coil l. A movable armature 6 is also arranged in the center opening of the spool 4 axially beyond'the stationary core piece 5 and so mounted as to permit limited movement of the armature toward and away from the stationary core piece 5.

In the embodiment shown in the drawing, the stationary core piece 5 is provided with an annular recess 1 both sides of which are tapered at an angle approximately 11 from parallel with the direction of movement of the armature. The armature 6 is provided with an annular projection 8 whose sides are doubly tapered to correspond with the taper of the sides of the recess 1 and the projection 3 is arranged to enter the recess 1 upon energization of the coil i. As shown, the bottom surface 9 of the recess '5 is blunt, as distinguished from knife-edge, so as to provide a substantial surface transverse to the direction of flux travel in the core. Similarly the tip Ill of the doubly tapered armature '5 is blunt to provide a substantial surface area transverse to the direction of flux travel.

It will be understood that both the yoke 5 and the armature B are constructed of magnetic material, but in the embodiment shown, the armature is provided with a stem 1 I of non-magnetic material extending through an aperture [2 in the yoke 5 to the exterior of the device. The stem H thus constitutes not only a guide for controlling the movement of the armature 6 but also constitutes the mechanical means for communicating the force of armature 6 to mechanism to be actuated by the solenoid.

As pointed out hereinabove it is important in a device of the character described to proportion the magnetic circuit in such manner that the maximum flux density occurs in the region of recess and projection ii and consequently in the embodiment shown in the drawing, the coil i is provided with an external casing i3 having end plates i4 anc, As shown, the circumferential casing [3 consists of but one thickness of material, the respective end plates i and iii consist of several thicknesses so that, as the radius of the magnetic path decreases, the cross section of magnetic material through which the magnetic flux is intended to travel does not decrease and accordingly the flux density does not increase. For example, if, in the embodiment shown in the drawing, it is assumed that the core 5 is one inch in diameter and the casing i3 is two inches in diameter and oils-sixteenth inch thick, it will be apparent that crcss-sectional of the casing it through which the magnetic flux travels is slightly in excess of the cross-sectional area of the stationary core ii through which the flux passes. however, the end plates i and i5 were constructed of the same thickness of material as the casing i it will be understood that, due to their diminish ing diameter as they approach the core greater flux density would be encountered and conse quently the present invention contemplates the provision of laminae it of magnetic material, three of which are shown to increase the cross section of the magnetic path at the end surfaces of the device. As shown these laminae are pro vided with openings to accommodate the terminal posts 2 and but with the exception thereof the laminae are uninterrupted. Similarly, at the other end of the device, the laminae i! may be provided for the same purpose. The outermost lamina ii is, in the embodiment shown, provided with'a dome iii to accommodate and limit move-- ment of the movable armature 5. While in the embodiment shown in the drawing the laminae iii and ii are shown as all of the same diameter, it will be understood that, if desired, in order to save material, a stepped arrangement may be employed with thickness increasing as the axis is approached.

In order to insure against magnetic freezing of the armature, suitable non-magnetic bumpers i9 may be provided in the end thereof for direct contact with the interior of dome iii. Similarly, a sleeve iii of non-magnetic material surrounds the cylindrical surface of armature 6 to separate it from direct contact with the end structure of the device. For the same purpose a spec-- ing means, such as a washer 2 i, of non-magnetic material is provided about the stem il within the depression formed by the annular projection 8 so as to prevent the armature E or any part thereof from coming into direct contact with the stationary core 5, in other words to insure the maintenance of an air gap between.

The arrangement of cooperating recess and projection in the stationary core and movable armature, respectively, is such as to accomplish the delivery of maximum pull near the beginning of the movement of the armature from its deenergized position as shown. For the device constructed on the proportions shown by the drawing (full scale) the maximum force is delivered by the armature when the projection 8 is in the position indicated by broken lines in Figure 1, that is, when the tip thereof is just entering the mouth of the recess 7, but this position of maximum pull may be varied by varying the inclinaell) tion of the taper, the depth of the recess or the width of the faces 9 and ill. It is significant that a device constructed in accordance with the present invention is capable of delivering a pull of approximately 36 pounds near the beginning of its operative movement (i. e. when the tip of the projection ii is about to enter the mouth of depression 7) when energized at 24 volts and 5.5 amperes, while to accomplish such a pull with similar devices, heretofore used employing a chamfered armature, a current on the order of i3 amperes at 24 volts was required.

rom the foregoing description those skilled in the art will readily understand the operation f the device and appreciate the significance thereof.

While a complete disclosure of one embodiment has-been given, it is realized that many modifications, variations and alterations will occur to those skilled in the art as the principle of the present invention is adapted and applied and it is therefore to be distinctly understood that the invention is not limited to the details of the foregoing disclosure which is for illustrative purposes only.

Having thus described the invention what is claimed is:

1. An electronnagnet comprising, an annular coil, a stationary yoke of magnetic material ineluding a part extending exteriorly about the coil to provide a continuous external flux path and extending centrally of the coil to provide part only of an interior flux path, said central part terminating in a doubly tapered face, and an axially movable core piece disposed centrally of the coil to complet the interior flux path, said core piece having its side surfaces parallel with its axis and terminating in a doubly tapered face, the doubly tapered faces on said parts being of a size and shape complemental to each other and arranged to internest upon energization of the electro-magnet whereby the pull of said electromagnet throughout the operative stroke of the movable core piece is substantially uniform.

2. An electro-lnagnet comprising, an annular coil, a stationary yoke of magnetic material including a part extending exteriorly about the coil to provide a continuous external flux path and a part extending centrally of the coil to provide part only of an interior flux path, said central part terminating in a face having a doubly tapered recess, and an axially movable core piece disposed centrally of the coilto complete. the interior flux path, said core piece having its side surfaces parallel with its axis and terminating in a face having a doubly tapered projection, the doubly tapered recess and doubly tapered projection being of a siz and shape complemental to each other and arranged to internest upon energization of the electron-magnet whereby the pull of said electromagnet throughout the operative stroke of the movable core piece is substantially uniform.

3. An electrmmagnet comprising, an annular coil, a stationary yoke of magnetic material including a part extending exteriorly about the coil to provide a continuous external flux path and a part extending centrally of the coil to provide part only of an interior flux path, said central part terminating in a doubly tapered face, and an axially movable core piece disposed centrally of the coil to complete the interior flux path, said core piece having its side surfaces parallel with its axis and terminating in a doubly tapered face, one of said doubly tapered faces being formed as a recess, and the other as a projection whose size and shape are complemental to that of the recess, and arranged to internest with the recess upon energization of the electro-magnet, means for guiding and confining the movement of said movable core piece so that when the electro-magnet is de-energized the projection on one of said tapered faces is entirely outside of and substantially beyond the recess in the other of said tapered faces whereby the pull of said electro-magnet throughout the operative stroke of the movable core piece is substantially uniform.

4. An electro-magnet comprising, an annular coil, a stationary yoke of magnetic material including a part extending exteriorly about the coil to provide a continuous external flux path and a part extending centrally of the coil to provide part only of an interior flux path, said central part terminating in a doubly tapered face, and an axially movable core piece disposed centrally of the coil to complete the interior flux path, said core piece having its side surfaces parallel with its axis and terminating in a doubly tapered face, the doubly tapered faces on said parts being of a size and shape complemental to each other and arranged to internest upon energization of the electro-magnet, the angle of taper of said tapered faces being substantially 15 or less from parallel with th direction of movement of the movable core piece whereby the pull of said electro-magnet throughout the operative stroke of the movable core piece is substantially uniform.

5. An electro-rnagnet comprising, an annular coil, a stationary yoke of magnetic material including a part extending exteriorly about the coil to provide a continuous external flux path and a part extending centrally of the coil to provide part only of an interior flux path, said central part terminating in a doubly tapered face, and an axially movable core piece disposed centrally of the coil to complete the interior flux path, said core piece having its side surfaces parallel with its axis and terminating in a doubly tapered face, one of said doubly tapered. faces being formed as a recess, and the other as a projection whose size and shape are complernental to that of the recess, and arranged to internest with the recess upon energization of the electro-magnet, the end of the projection being blunt to provide a substantial area transverse to the direction ofthe flux path thereat whereby the pull of said electro-magnet throughout the operative stroke oi the movable core piece is substantially uniform LAWRENCE M. PERSONS. 

